The invention is based on a fuel injection pump as defined hereinafter.
In reciprocating slide pumps of this kind, known for instance from European Patent Document 0 261 156 Al, the quantity and injection onset control are effected by the control of conduits by way of which the pump work chamber can be made to communicate with the suction chamber of the pump, namely by the association of control edges located on the pump piston with control edges located on the control slide.
This kind of fuel injection pump, which is predominantly used in so-called in-line reciprocating pumps of multicylinder engines, is known per se.
It is also known that an essential influence on economy and on the mixture and exhaust emissions of direct-injection utility vehicle Diesel engines is exerted by the fuel injection onset and injection duration, which must be adhered to exactly. The increased injection pressures that are necessary, because of the requisite high moment to be transmitted by the injection adjuster, to achieve a short injection duration with good fuel atomization make increasingly stringent demands of this drive element. At the same time, a need also exists for a wider adjusting range and a more compact structure. Conventional mechanical injection timing adjusters are often unable to fully meet these demands; particularly in unsteady operation, the results are an unsatisfactory response and unstable operating states.
ATZ (Automobiltechnische Zeitschrift) [Automotive Engineering Journal] 91 1989, pp. 628 ff. attains this object, in conventional pumps, by providing that the pump piston is provided on its side toward the pressure chamber with a defined polished section; as a result, the rpm-dependent prefeeding phase is reinforced and utilized for adjusting the supply onset and correcting the course of fuel quantity.
Temperature-dependent triggering this generic type of reciprocating slide is effected by black/white triggering of the reciprocating slide as a function of the cold-starting and warmup phases. Beyond this control, however, for the reasons given above, it is also desirable to assure a load- and rpm-dependent adjustment of the injection onset by the simplest possible means.